Roy Oswalt is worried about his back problems forcing him into retirement, so it’s no surprise that the Phillies have placed him on the disabled list before even waiting for the results of the MRI exam scheduled for Monday.

There seems to be a legitimate fear that he’ll never pitch again and if he does come back it certainly won’t be within two weeks, so the DL stint was a no-brainer. Scott Mathieson replaced Oswalt on the roster.

Along with putting Oswalt on the shelf the Phillies also released J.C. Romero, who predictably passed through waivers unclaimed after they designated him for assignment last week. Between his $1.35 million salary and disastrous numbers versus right-handed hitters Romero simply wasn’t worth a waiver claim and will probably have to work his way back to the majors on a minor-league contract. He’s merely a left-handed specialist at this point.

Paxton, 30, has been among the game’s better starters over the past few years. In 2018, he went 11-6 with a 3.76 ERA and a 208/42 K/BB ratio in 160 1/3 innings. The lefty has two more years of arbitration eligibility remaining after earning $4.9 million this past season.

Sheffield, 22, is the headliner in the Mariners’ return. He made his major league debut in September for the Yankees, pitching 2 2/3 innings across three appearances. Two of those appearances were scoreless; in the third, he gave up a three-run home run to J.D. Martinez, certainly not an uncommon result among pitchers. MLB Pipeline rates Sheffield as the Yankees’ No. 1 prospect and No. 31 overall in baseball.

Thompson-Williams, 23, was selected by the Yankees in the fifth round of the 2016 draft. This past season, between Single-A Charleston and High-A Tampa, he hit .299/.363/.546 with 22 home runs, 74 RBI, 63 runs scored, and 20 stolen bases in 415 plate appearances. He was not among the Yankees’ top-30 prospects, per MLB Pipeline.

Swanson, 25, was selected by the Yankees in the eighth round of the 2014 draft. He spent most of his 2018 campaign between Double-A Trenton and Triple-A Scranton/Wilkes-Barre. Overall, he posted a 2.66 ERA with a 139/29 K/BB ratio in 121 2/3 innings. MLB Pipeline rated him No. 22 in the Yankees’ system.

This trade comes as no surprise as the Yankees clearly wanted to upgrade the starting rotation and the Mariners seemed motivated to trade Paxton this offseason. To the Mariners’ credit, they got a solid return for Paxton, as Sheffield likely becomes the organization’s No. 1 prospect. The only worries about this trade for the Yankees is how Paxton will fare in the more hitter-friendly confines of Yankee Stadium compared to the spacious Safeco Field, and Paxton’s durability. Paxton has made more than 20 starts in a season just twice in his career — the last two years (24 and 28). The Yankees are likely not done adding, however. Expect even more new faces before the start of spring training.